Discount telephone billing plans have become commonplace. In a typical plan, a customer receives a discount on all calls made if total usage exceeds a predefined time or monetary limit. Such discount billing plans have been extended to organizational customers, such as companies and universities, which have multiple individuals placing calls, but which have only one billing account. Groups of customers who have separate billing accounts have been unable to participate in discount billing plans as a group because there is no way that calls made by such customers can be priced based on the group calling plan and on the usage by other members of the group.